In recent years laminates for use as wound dressings have become available which are based on polyurethane films. The film may contain or act as a carrier for substances such as silver salts or alginates which act as bacteriostats or which promote healing.
Film dressings of this nature have considerable advantages in two respects. First, they can readily be produced in transparent form and thus allow the condition of the wound to be monitored without removing the dressing. Secondly, they can be produced in microporous forms which allow movement of water vapour to the exterior of the dressing and movement of air to the interior of the dressing, while preventing movement of bacteria through the dressing; this is of benefit in treating exuding wounds such as burns.
Film dressings presently in use, however, have the disadvantage that they are difficult to apply. It is usual for a film dressing to have an adhesive layer for application to the skin of the patient, the adhesive layer being initially covered by a release paper. Once the release paper is removed from the adhesive layer, the film is delicate and difficult to handle. Stretching of the film can destroy its barrier integrity, while a lack of tension during application can lead to wrinkling. For these reasons, most film dressings currently used are provided with a stiffened edge or frame on the outer face, which stiffening must be removed after the dressing has been applied. These arrangements, however, lead to undesirable complexity, waste of material, and increased expense.